1. Field of the Invention
The present invention relates to a light emitting apparatus and a control method thereof. More particularly, the present invention relates to a light emitting apparatus which controls a plurality of LEDs.
2. Description of the Related Art
Generally, a light emitting apparatus comprises a plurality of light emitting parts such as an LED array arranged in a matrix pattern and a display part such as a liquid crystal display (LCD) panel. The plurality of light emitting parts function as a light source to display a predetermined image on the display part.
FIGS. 1a and 1b illustrate an example of a conventional light emitting apparatus. As shown in FIG. 1a, a light emitting apparatus 1a comprises nine LEDs 10a to 10c, 20a to 20c, and 30a to 30c and driving circuits 11a to 11c, 21a to 21c and 31a to 31c which respectively control the nine LEDs 10a to 10C, 20a to 20c and 30a to 30c. The light emitting apparatus 1a may sequentially control a brightness level of the nine LEDs 10a to 10c, 20a to 20c and 30c to 30c through the driving circuits 11a to 11c, 21a to 21c and 31a to 31c. The nine LEDs 10a to 10c, 20a to 20c, and 30a to 30c may comprise a single color or various colors through a mixture of certain colors of the LEDs.
As the driving circuits 11a to 11c, 21a to 21c and 31a to 31c which are respectively distributed to the nine LEDs 10a to 10c, 20a to 20c, and 30a to 30c receive a signal i1, i4, i7; i2, i5, i8 and i3, i6, i9 respectively, the light emitting apparatus 1a may drive the respective LEDs 10a to 10c, 20a to 20c and 30a to 30c to emit light in a certain brightness level or to realize a desired image.
However, with this configuration, the greater the number of the LEDs, the greater the number of the driving circuits and the driving signals. When the LEDs are arranged in the same density, the number of driving circuits and driving signals increases in proportion to a square of an area, thereby causing impracticability.
As shown in FIG. 1b, a light emitting apparatus 1b comprises nine LEDs 12a to 12c, 22a to 22c and 32a to 32c which are arranged in three columns and three rows, three driving circuits 13a to 13c which control respective columns of the nine LEDs 12a to 12c, 22a to 22c and 32a to 32c and three switches 14, 24 and 34 which control respective rows of the nine LEDs 12a to 12c, 22a to 22c and 32a to 32c. 
The light emitting apparatus 1b sequentially turns on the three switches 14, 24 and 34 at predetermined time intervals, and supplies a driving current i1, i2 and i3 corresponding to the respective LEDs 12a to 12c, 22a to 22c and 32a to 32c which are disposed in the turned-on row to emit light. After the LEDs 32a to 32c in the last row emit light, the light emitting apparatus 1b drives the LEDs 12a to 12c in the first row to emit light again. When the LEDs in the respective rows are sequentially driven at a fast speed, the human eye does not recognize the change of the light, but recognizes average brightness of the changing light (hereinafter, referred to as “brightness”). Thus, a user may feel that the respective LEDs are simultaneously driven in different brightness.
With this configuration, the number of driving circuits and driving signals corresponds to the number of rows of LEDs, thereby simplifying a circuit configuration. However, there is only one row of LEDs that continuously emit light, thereby lowering the efficiency of the LEDs. The human eye recognizes at best the brightness of the LEDs which is divided by the number of rows. To overcome such a disadvantage, switches may be provided in pairs or in groups, thereby simultaneously driving the LEDs in the rows included in the respective groups. However, in this case, the number of driving circuits and driving signals increases as the number of the groups increases.
Accordingly, there is a need for an improved light emitting apparatus having a simplified circuit configuration and improved efficiency that can drive light emitting parts to independently emit light at various brightness levels.